Carl hoffmann



(No Model.)

C. HOFFMANN.

GOMMUTATOR. No. 520,264. v Patented May 22,1894.

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IN VEN TOR AAAAAAAAAAAAA c.

UNITED STATES PATENT OFFICE.

OARL HOFFMANN, OF BERLIN, GERMANY, ASSIGNOR TO SIEMENS & HALSKE, OF SAMEPLACE.

COMMUTATOQR.

SPECIFICATION forming part of Letters Patent No. 520,264, dated May 22,1894.

Application filed September 28, 1893- Serial No. 486,667. (No model.)

To caZZ whom it may concern.-

Be it known that I, CARL HOFFMANN, a subect of the King of Prussia,German Emperor, residlng at the city of Berlin, Kingdom of Prussia,German Empire, have invented new and useful Improvements in Commutators,of which the following is a specification.

This invention relates to commutators for dynamo electric machines ingeneral, and particularly to the bars and the particular construction ofthe hub thereof, and it has for its object to provide a device of thisnature which shall overcome the objections to those now in use.

As commutator bars have been and are at present made, they consist of abody having a downwardly projecting portion of such construction as toallow of its being rigidly secured in place in the commutator, but when,however, the bar has been once located, it has been impossible to removeit for repairs or other cause, without seriously injuring and sometimesdestroying the insulation of the hub. The usual bar has moreover, at itsinner end an upwardly projecting portion provided with a slot or othermeans for the reception of the end of its respective armature Windingwhich end is then surrounded and securely fastened therein by means ofsolder or other suitable sealing and conducting substance. Herein lies asecond objection in that to remove the bar it is also necessary toremove the end of the winding secured there- 111, which is a difficulttask and one attended by liability to injury of the bar and armature.

In the accompanying drawings forming a part of this specification:Figure 1 is a longitudinal sectional view of a commutator hub, showingits shaft in elevation, and the arrangement. and location of theelements of.

the compound bar. Fig. 2 is a section of the contact element of the barand its key. Fig. 3 is a front end view of the hub having portionsthereof broken to show the location and arrangement of the bars and alsothe position and manner of securing the keys in place.

The commutator hub used in connection with my invention is formed of theusual material and is of the usual construction with the exception ofthe outer end thereof which is provided with an annular projection orfiange 72 and having a shoulder i thereon, the former having a number ofthreaded perforations 70 for the reception of key-screws Z, which mayact in conjunction with the spline m to prevent'revolution anddisplacement of the hub with reference to the armature shaft n. Theshoulder 11 is also provided with threaded perforations for a purpose aswill be hereinafter set forth.

My commutator bar consists of a ground portion a, which may be made ofcopper or other metal and of a depth less than that of the narrowedportion a: of the hub and having an upwardly extending slotted orperforated 6 5 lug bat its rear end for the reception of the end of itsrespective amature winding, which may be secured in place in the usualmanner. The initial portion of the lug b has an outward slant forming anangle 0 to fit into and be held within a corresponding re-entrant angleat in the annular projection 01' of the hub. The inclination of the saidportion also has the effect to establish a re-entrant angle e for thereception and retention of the inner end of the contact element of thebar. This contact element consists of abar g which may be made of asuitable metal or of carbon or of any other suitable mineral, thelongitudinal vertical section thereof having a trapezoidal form as isshown in Fig. 2 of the drawings.

In securing each of my bars 9 to their respective backings a, I use akey 0, shown in Fig. 2, which is of a form to lie against the innersurface of flange hand to rest upon the upper surface of shoulder t' towhich I secure it, preferably by means of a screw 19 passed through itand into the portion c' which is provided with a threaded perforation rfor go the reception thereof. The inner side of the key 0 is formed tocorrespond to and lie snugly against the outer end 3 of the contact barg, when brought into position through the medium of screwp.

In assembling the elements of my invention, it is my practice to apply asuitable insulation t entirely around the narrowed portion of the huband of such a width as to extend upwardly and beyond the annular 10oflanges thereof. A base bar a is then put into position, it being of alength slightly less than the distance between the flanges of the hub,to facilitate its adjustment. A contact bar g, having its under surfaceformed to lie snugly against and in intimate electrical contact with itsrespective base bar, is then placed into position as shown in Fig. 1,its inner end entering and being held within the opening (key) 0 of thebar a. The bar 9 is slightly longer than the upper surface of bar a, asis shown. A keyo is then put into position between the outer end of thebar 9 and the flange h, the projecting portion of the insulation beingforced over to lie between and thoroughly insulate them. A screw 19 isthen turned into place and firmly holds the several elements in theirseveral positions. A strip of insulating material u is then placed oneither side of the compound bar and asec- 0nd couple is then secured inplace. This procedure is continued until the several bars are located,when the commutator is keyed to its shaft and the ends of the armaturewindings are secured in their respective places. The narrowed portion ofthe hub is provided with an annular depression to forming a means forthe insertion of a tool beneath the base bar to assist in its removalfrom the hub.

Having now described my invention and the manner of assembling the partsthereof, I do declare that what I claim is 1. The combination with acommutator bar comprising separable elements, of an individual retainingkey common tothe bar and the separate elements thereof.

2. The combination with a commutator bar comprising a base bar and acontact bar, of a common retaining key therefor.

3. The combination with a commutator bar comprising a base bar and aremovable contact bar, of a common retainingkey therefor.

4. The combination with a commutator bar comprising a base bar havingmeans for the attachment of its armature winding, and a contact bar; ofa common retaining key therefor.

The combination with a commutator bar composed of separable elements, ofan ad usting and retaining key therefor.

6. The combination with a compound commutator bar, of a deviceforretaining the elements in their respective positions, said devicebeing insulated from the elements of the bar.

'7. The combination with a commutator bar of a hub therefor,havinganarrowed portion provided with an annular depression for thereception of means for the removal of said bar, as set forth.

8. A commutator, consisting of a shell; removable base bars securedthereto and insulated therefrom; removable contact bars; and aninsulated retaining key for each pair of said bars, seated in saidshell.

9. A commutator bar consisting of a metallic base bar and a contact barof greater refractoriness.

10. A commutator bar consisting of a metallic base bar and a carboncontact bar.

In testimony whereofIaffiX mysignature in the presence of two witnesses.

CARL HOFFMANN.

Witnesses:

OSCAR BIELEFELD, JOHN B. JACKSON.

